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Old 06-28-2014, 04:25 PM   #1
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Question 1990 5.7 Chevy Idle Surge

Hey folks. I'm having some issues with my truck not running right. When I first start it up it idles fine. After a few minutes the idle surges and sometimes the truck quits. I checked the fuel pressure and it holds steady at 12psi during the surging. Vacuum is at 20 in hg on the gauge until it starts surging then the gauge goes up and down with the surge. I replaced the coolant temp sensor, but that didn't fix it. TPS and IAC sensors came new on the Holley TBI last year. O2 sensor and mass airflow are new also.

I monitored the truck while it was running with my computer and the "block learn multiplier" flashes red and reads around 160 when its surging.

I have no idea what else to check so any help is appreciated.
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Old 06-30-2014, 01:32 PM   #2
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i would guess something with the egr, its a pretty common issue on those and symptoms sound like vacuum leak. you could block it off to see if it runs better
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